A disc brake system may include a brake disc or rotor fixedly mounted on an axle hub of a vehicle, and a brake caliper having brake pads that are selectively urged against the opposing sides of the rotor to stop or slow rotation of the rotor and wheel on which it is mounted. Typically, the rotor is attached directly to, or directly interfaces with, the axle hub with no intermediate structure. This may limit the material properties of the interface between the rotor and axle hub to those properties of the axle hub itself
A disadvantage of such designs is that the rotor and axle hub may be made of materials having different coefficients of thermal expansion, and/or may be heated to different temperatures during braking, so that the connecting portions of the axle hub and rotor will expand and contract at different rates or by different amounts. This differential in amount expansion and contraction places stresses on the portions of the axle hub and rotor forming the connection between the two. Another disadvantage of a direct interface between the rotor and axle hub is that heat from the rotor can be conducted directly into the bearing/grease or adjacent oil seal area. This prolonged heat can have a detrimental effect on both bearing and seal life.
Yet another disadvantage of such designs is that should a splined axle hub become worn or damaged, it is necessary to replace the axle hub at great time, expense, and downtime of the associated vehicle. Splined or other connections between the axle hub and rotor that accommodate relative expansion and contraction require costly machining of such features as splines and grooves, which greatly adds to the cost of the disc brake assembly. This is especially true if a hardened material is selected for the axle hub.
Accordingly, there is a need for a system that accommodates relative expansion and contraction of the axle hub and rotor, and yet is relatively simple and inexpensive to fabricate. There is also a need to have the flexibility of use of various materials as an interface between the rotor and the axle hub for both weight considerations as well as strength. Isolation of the interface of the rotor to hub joint away from the bearing/seal area will significantly improve system longevity and performance.